diff --git a/src/api/serverproxy_manager.py b/src/api/serverproxy_manager.py
index da67268..5cb48b4 100644
--- a/src/api/serverproxy_manager.py
+++ b/src/api/serverproxy_manager.py
@@ -26,7 +26,7 @@ class ServerProxyManager:
     @classmethod
     def get_proxy_for_hostname(cls, hostname):
         found_proxy = cls.server_proxys.get(hostname)
-        if not found_proxy:
+        if hostname and not found_proxy:
             new_proxy = RenderServerProxy(hostname)
             new_proxy.start_background_update()
             cls.server_proxys[hostname] = new_proxy
diff --git a/src/engines/core/base_engine.py b/src/engines/core/base_engine.py
index 0cf4d27..92da42e 100644
--- a/src/engines/core/base_engine.py
+++ b/src/engines/core/base_engine.py
@@ -13,7 +13,7 @@ class BaseRenderEngine(object):
 
     def __init__(self, custom_path=None):
         self.custom_renderer_path = custom_path
-        if not self.renderer_path():
+        if not self.renderer_path() or not os.path.exists(self.renderer_path()):
             raise FileNotFoundError(f"Cannot find path to renderer for {self.name()} instance")
 
     def renderer_path(self):
diff --git a/src/engines/core/base_worker.py b/src/engines/core/base_worker.py
index bfdce4c..c3fa603 100644
--- a/src/engines/core/base_worker.py
+++ b/src/engines/core/base_worker.py
@@ -72,6 +72,7 @@ class BaseRenderWorker(Base):
         self.parent = parent
         self.children = {}
         self.name = name or os.path.basename(input_path)
+        self.maximum_attempts = 3
 
         # Frame Ranges
         self.project_length = -1
@@ -193,8 +194,15 @@ class BaseRenderWorker(Base):
             while True:
                 # Log attempt #
                 if attempt_number:
-                    f.write(f'\n{"=" * 80} Attempt #{attempt_number} {"=" * 30}\n\n')
-                    logger.warning(f"Restarting render - Attempt #{attempt_number}")
+                    if attempt_number >= self.maximum_attempts:
+                        err_msg = f"Maximum attempts exceeded ({attempt_number})"
+                        logger.error(err_msg)
+                        self.status = RenderStatus.ERROR
+                        self.errors.append(err_msg)
+                        return
+                    else:
+                        f.write(f'\n{"=" * 80} Attempt #{attempt_number} {"=" * 30}\n\n')
+                        logger.warning(f"Restarting render - Attempt #{attempt_number}")
                 attempt_number += 1
 
                 # Start process and get updates
diff --git a/src/engines/engine_manager.py b/src/engines/engine_manager.py
index 944057a..9edf4b6 100644
--- a/src/engines/engine_manager.py
+++ b/src/engines/engine_manager.py
@@ -211,8 +211,8 @@ class EngineManager:
             raise FileNotFoundError(f"Cannot find any installed {renderer} engines")
 
         # Find the path to the requested engine version or use default
-        engine_path = None if engine_version else all_versions[0]['path']
-        if engine_version:
+        engine_path = None
+        if engine_version and engine_version != 'latest':
             for ver in all_versions:
                 if ver['version'] == engine_version:
                     engine_path = ver['path']
@@ -225,6 +225,9 @@ class EngineManager:
                     raise FileNotFoundError(f"Cannot download requested version: {renderer} {engine_version}")
                 engine_path = download_result['path']
                 logger.info("Engine downloaded. Creating worker.")
+        else:
+            logger.debug(f"Using latest engine version ({all_versions[0]['version']})")
+            engine_path = all_versions[0]['path']
 
         if not engine_path:
             raise FileNotFoundError(f"Cannot find requested engine version {engine_version}")
diff --git a/src/engines/ffmpeg/ffmpeg_worker.py b/src/engines/ffmpeg/ffmpeg_worker.py
index b7780fd..49fc80c 100644
--- a/src/engines/ffmpeg/ffmpeg_worker.py
+++ b/src/engines/ffmpeg/ffmpeg_worker.py
@@ -17,7 +17,7 @@ class FFMPEGRenderWorker(BaseRenderWorker):
 
     def generate_worker_subprocess(self):
 
-        cmd = [self.engine.default_renderer_path(), '-y', '-stats', '-i', self.input_path]
+        cmd = [self.renderer_path, '-y', '-stats', '-i', self.input_path]
 
         # Resize frame
         if self.args.get('x_resolution', None) and self.args.get('y_resolution', None):
@@ -29,7 +29,7 @@ class FFMPEGRenderWorker(BaseRenderWorker):
             cmd.extend(raw_args.split(' '))
 
         # Close with output path
-        cmd.append(self.output_path)
+        cmd.extend(['-max_muxing_queue_size', '1024', self.output_path])
         return cmd
 
     def percent_complete(self):
diff --git a/src/ui/add_job.py b/src/ui/add_job.py
index cd53446..bbae15b 100644
--- a/src/ui/add_job.py
+++ b/src/ui/add_job.py
@@ -186,6 +186,7 @@ class NewRenderJobForm(QWidget):
         # Version
         renderer_layout.addWidget(QLabel("Version:"))
         self.renderer_version_combo = QComboBox()
+        self.renderer_version_combo.addItem('latest')
         renderer_layout.addWidget(self.renderer_version_combo)
         renderer_group_layout.addLayout(renderer_layout)
         # dynamic options
@@ -248,6 +249,7 @@ class NewRenderJobForm(QWidget):
         # load the version numbers
         current_renderer = self.renderer_type.currentText().lower() or self.renderer_type.itemText(0)
         self.renderer_version_combo.clear()
+        self.renderer_version_combo.addItem('latest')
         self.file_format_combo.clear()
         if current_renderer:
             renderer_vers = [version_info['version'] for version_info in self.renderer_info[current_renderer]['versions']]
@@ -442,7 +444,7 @@ class SubmitWorker(QThread):
         hostname = self.window.server_input.currentText()
         job_json = {'owner': psutil.Process().username() + '@' + socket.gethostname(),
                     'renderer': self.window.renderer_type.currentText().lower(),
-                    'renderer_version': self.window.renderer_version_combo.currentText(),
+                    'engine_version': self.window.renderer_version_combo.currentText(),
                     'args': {'raw': self.window.raw_args.text()},
                     'output_path': self.window.output_path_input.text(),
                     'start_frame': self.window.start_frame_input.value(),